This invention relates generally to combination locks and more particularly, it relates to a system for changing the combination of such locks.
Most prior art combination locks rely on having tumbler wheels with gates thereon. When the proper combination is dialed, an arm fits into the gates. Depending on the construction of the lock, when the arm falls into the gates, the latch can be released, or when the arm falls into the gates, it can abut a pawl connected to the dial whereby further rotation of the dial pulls the arm to open the latch.
In such locks, the tumbler wheels are normally two pieces, an inner drive member and an outer gate ring. Means are provided for connecting the two parts of the tumbler wheel together. The position of the gate rings when they are aligned is always the same for each lock, no matter what the chosen combination is. Different combinations are obtained by changing the orientation of each drive member in the gate ring because the drive members are fixed to the combination dial.
Many combination locks have a mechanism for releasing the gate ring from the drive member to change the combination of the lock. In order to accomplish this, however, many tumbler wheels are relatively complex. For example, Murphy, U.S. Pat. No. 901,116 (1908) is somewhat typical of common tumbler wheels. The outer gate ring is a hollow casting surrounding a toothed drive member. A spring arm is inserted in the hollow casting and teeth on the arm engage the teeth on the inner drive member. A camming member is also inserted in the hollow casting, and by rotating the cam, the arm is urged away from or against the inner drive member. Because of their complexity, such tumbler wheels are relatively expensive to manufacture. Parts on the gate ring must be machined to relatively tight tolerances so that they will properly fit together. Moreover, parts must be assembled within the gate ring. One object of the present invention is to provide a lower cost gate ring to eliminate the necessity of the machining and assembly steps of the prior art.
One-piece gate rings have been proposed. For example, the gate ring in Brettell, U.S. Pat. No. 145,618 is made of elastic material that urges itself against the drive ring. The gate is formed where the ring is split at its ends. The device eliminates some of the problems associated with machined gate rings. However, it and the machined gate rings suffer from another problem. In order to change combinations, the gate ring must be released from the drive member. When the gates are aligned, a corresponding portion of each gate ring is aligned with an opening through the case. A key or tool is inserted through the opening to engage a cam or otherwise to open the gate ring. In devices such as Murphy, the key is inserted into a cam, and turning the cam allows the arm on the gate ring to move out of engagement with the drive member thereby releasing it. Rotating the cam back to its original position urges the arm into engagement with the drive member. In the Brettell reference, a tool is inserted between opposing portions of the gate ring, and when turned, it overcomes the resiliency of the gate ring to release it from the drive member. However, the resiliency of the gate ring tends to urge the key back to its initial position permitting the gate ring to engage the drive member and preventing adjustment of the combination. Therefore, it is an object of the present invention to overcome the problem by eliminating extra cams and by designing the gate ring release in such a manner that the resilient arm will not urge the arm back to its gripping position when the key is rotated to the arm release position.
Another problem associated with changeable combination locks is removal of the key from the back of the case while the gate rings on any of the tumblers are released from their associated drive rings. If this occurs, it would be possible to have a drive member that could slip in its connection with the gate ring. That occurrence would misalign the gate ring with the dial, and it would be impossible to again align the gates thereby aligning the cams or gate ring opening so that the gate ring could be secured to the drive member. Thus, the lock would be rendered useless.
Therefore, it is another object of the present invention to disclose and provide a combination lock permitting removal of the key only when the gate ring is secured to the drive member. Of course, it is an object of the present invention to construct a combination lock which is both reliable and low cost and which eliminates problems occurring in the prior art. These objects are met by the present invention which also meets other objects that, although not set forth specifically herein, are evident from the description of the invention.